Coal dissolving process

ABSTRACT

A process for dissolving sub-bituminous coal by heating a slurry of said coal in a hydrogenated anthracene oil in the presence of gaseous carbon monoxide, water, and hydrogen at a temperature of from about 400* to about 425*C. and at a total pressure of from about 2,000 to about 5,000 p.s.i.g.

A United States Patent [191 Seitzer et al.

[ COAL DISSOLVING PROCESS [75] Inventors: Walter H. Seltzer, Chester; Robert W. Shinn, Aston, both of Pa.

[73] Assignee: Sun Research and Development Co.,

Philadelphia, Pa.

[22] Filed: Sept. 16, 1971 21 Appl. No.: 181,229

[52] US. Cl. 208/8 [51], Int. Cl. Ql Qg l /QQ [58] Field of Search 208/8 [56] References Cited UNlTED STATES PATENTS 3,594,304 7/1971 Seitzer 208/8 3,642,607 2/1972 sealer 208/8 OTHER PUBLICATIONS Appell, H. R.; Wender, 1.; Miller R. D., Sol ulgiflgatign [111 3,819,506 June 25, 1974 of Low Rank Coal with Carbon Monoxide and wa..

ter, Chemistry and Industry, No. 47, Nov. 22, 1969-,

Primary Examiner-Delbert E. Gantz Assistant Examiner-James W. Hellvvege Attorney, Agent, or FirmMr. George Church; Mr.

Donald R. Johnson; Dr. Paul Lipsitz 57 ABSTRACT A process for dissolving sub-bituminous coal by heat-I ing a slurry of said coal in a hydrogenated anthracene oil in the presence of gaseous carbon monoxide, wa-

3 Claims, No Drawings l COAL DISSOLVING PROCESS Numerous coal liquefaction processes are well known in the art. Forexample, U.S. Pat. No. 2,686, l52

discloses a lignitic coal extraction process carried out with an organic solvent such as Tetralin or a mixture thereof with a phenol at temperatures between about 480F. (249C) and about 900F. (460C) with or without hydrogen being used, and at atmospheric or at autogenous hydrogen pressure. This prior art disclosure indicates that liquid products are. formed in an amount ranging from about '7 percent to about 50 percent. Such a procedure cannot economically lend itself toward commercial production of liquid products, since what is needed in any commercial coal liquefaction process is essentially complete liquefaction of the coal.

Recently, as disclosed in U.S. Pat. No. 3,594,304 (Seitzer and Shinn, assigned to Sun Oil Co., issued July 20, 197 1) a coal liquefaction process for subbituminous coal has been found which is able to achieve solution of 90 percent or more of the coal. This is accomplished bysubjecting a sub-bituminous coal to solution in a hydrogenated poly-nuclear solvent under pressure of hydrogen of from about 2,000 to about 3,000 p.s.i.g. and maintaining the temperature of the process within the narrow range 440 to 450C. for a period of about 5 to about minutes residence time. This .process is a significant improvement over previously available processes, but it does have an economic liability in that it requires the pressure of hydrogen used in the system to be rather high (2,000 to 3,000 p.s.i.g.) in order to achieve high dissolution of coal.

It is also known to convert sub-bituminous coal to benzene-soluble and volatile materials by use of a carbon monoxide and water atmosphere, but relatively low conversions are obtained by this technique. Thus, Appell and Wender (Reprints, Am. Chem. Soc., Div. of Fuel Chem., 156 Nat. Meeting, Sept. 1968; v. 12, No. 3, pp. 220-224) report that at 375 C. and short contact times, a conversion of 43 percent of subbituminous coal to benzene-soluble and volatile materials was obtained with carbon monoxide and water at a pressure of 4,200 p.s.i.g. With hydrogen at 5,700 p.s.i.g., the conversion was 27 percent. At 425C. the differencein conversion decreased, but still favored the carbon monoxide-water by a significant margin.

It has now been found that a high degree of subbituminous coal dissolution can be achieved without the Previously required high hydrogen pressures, and even at somewhat lower temperatures than that of U.S.

Pat. No. 3,594,304 referred to above, if the process is carried out in a gaseous atmosphere of hydrogen (at much lower pressure), carbon monoxide, and water.

- Thus, this invention comprises the'process of dissolving sub'bitu minous coal by heating a slurry of said coal in a solvent of anthracene oil hydrogenated to contain from about 7 percent toabout 9 percent hydrogen, in the presence of hydrogen, carbon monoxide, and water, at about 400 to about 425C. and at a total pressure of from about 2,000 to about 5,000 p.s.i.g.

As indicated, the coal used in the process of the invention will be a sub-bituminous coal and this will include lignite coals such as North Dakota lignite, Powder River Sub-bituminous Coal, and the like. As will be seen from the data which follow, a significant parameter in the process of the invention is the use of anthracene oil which has been-hydrogenated to contain about 7 percent to 9 percent by weight of hydrogen. The process is not operable with the anthracene oil obtained from commercial sources which contains about 5 percent to 6 percent hydrogen, but when such oil is hydrogenated, by any available technique, it becomes of value for use in this invention. It is believed that the hydrogenation to a hydrogen content of 7 percent to 9 percent does not proceed beyond the introduction of hydrogen into the center ring of the anthracene moiety in the anthracene oil. After use of the hydrogenated anthracene oil in the process it must be rehydrogenated in order to be useful in any recycle process. The amount of solvent used in theprocess may vary, but enough must be used to provide a stirrable slurry. Usually the amount of solvent used will be a weight ratio of oil to coal of about 1:1 to 5:1.

ln carrying out the process of the invention, a slurry of the powdered coal in the solvent is introduced into pressuring the reactor, the partial pressure of hydrogen should not be greater than, and preferably less than, the

partial pressure of carbon monoxide. In the process of the invention, the presence of the hydrogen does make a contribution to the coal dissolution efficiency, but the major contribution to solution is due to the carbon monoxide. Thus, from the standpoint of economics, the partial pressure of hydrogen should be small in comparison to that of the carbon monoxide partial pressure. As the contents of the reactor are stirred or agitated, the temperature is raised rapidly to the temperature range of 400 to 425C. and the total pressure rises to between about 2,000 to 5,000 p.s.i.g. The residence time for solution ofthe coal to occur is not critical and will pages 4-1 1 Typically, producer gas from coke made with oxygen contains on a percent by volume basis about 53 percent CO and about 31 percent hydrogen and such a gas is preferred. It will be understood that the composition of the producer gas used may be adjusted so as to provide the desired partial pressures of hydrogen and carbon monoxide in the pressure reactor used in subject invention, but with a gas such as described above, no such adjustment is necessary. Since producer gas may or may not contain water vapor, it may be adjusted to contain this component also, preferably in an amount such that the waterzCO molar ratio is from about 2:1 to 1:2, but, of course, water may be introduced into the reactor separately. The major advantage in using producer gas is that itprovides an economical source of reactant carbon monoxide and hydrogen and, furthermore, does not need to be refined for use in the process as the other components (CO 0 CH, and N do not interfere. Since, the process of the invention is uniquely suited to use of producer gas, it is particularly valuable in providing an economical coal dissolving process.

The dissolved coal formed by the process of the invention is a valuable product similar in many respects to a crude oil and is subjected to the usual refining operations to produce petroleum products. For use in this manner, the solution is merely filtered to remove the small amount of insoluble products present, and the filtrate treated in accord with conventional refinery techniques.

In order to more fully describe the invention, the following examples are given:

Liquefaction of coal is carried out in stirred pressure reactors which contains dry, powdered Big Horn Coal and the anthracene oil, the weightratio of liquid to coal being 2:1. An appropriate amount of water is added and the reactor is rapidly heated while agitating to a temperature of 415C. and held on temperature for '1 hour, cooled, and the insoluble material is filtered off.

I The table shows the results obtained under various comparative conditions.

Dissolution of Big Horn Coal Final hydrogen (Ex. 5). Examples 8 and 9 further illustrate the low degree of solution obtained withouthydrogen in normal anthracene oil, even at relatively high pressures.

EXAMPLE 10 In accord with the procedure of the above examples, a pressure reactor is charged with 80 g. of hydrogenated anthracene oil (7 percent hydrogen), g. of dry, powdered Big Horn Coal, 9 ml. water, and pressured to 600 p.s.i.g. with a dry producer gas made by passing oxygen and steam over coke and containing on a volume percent basis 53.3% C0, 30.9% H ,'l2.8%

CO 0.3% 0 0.4% CH and 2.3% N After heating at 425C, the total pressure rises to 2,500 p.s.i.g. and after 2 hours the reactor is cooled and the insolubles filtered off. It is found that 87% of the .coal is dissolved. I

It is clear fromthe'preceding experimental data that the proc'ess of the invention provides a means for effi- I ciently bringing coal into solution under economical A0 Anthracene Oil -5.7% H,

The effect SfTHEB' 'dFJgHatHhth'rach'dii'ifi "giv- 40 conditions and thus the process provides a valuable j ing high yields of soluble products is readily seen from the table. Comparing Example 1 and 2, it is seen that the reaction conditions are identical except for the solvent, yet the hydrogenated anthracene oil enabled 94 percent solubility of the coal to be achieved while only 64 percent was obtained with ordinary anthracene oil. Examples 3 to 5 also show high coal solubility in accord with the process of the invention and particular attention is called to Example 5 where high solubility is obtained at very low hydrogen pressure. As can be seen from Example 6, without CO and H 0 the coal solubility is low. Comparison of Example 5 and 7 indicates the value of hydrogen in the hydrogenated anthracene oil system, since CO and H 0 without hydrogen (Ex. 7) requires'high pressures (3,400 p.s.i.g.) to approach .the

solubility obtained at low pressures (2,000 p.s.i. g. with contribution to the art of coal solubilization.

The invention claimed is: v

1. A process for dissolving sub-bituminous coal which comprises heating a slurry of said coal in a hydrogenated anthracene oil containing from about 7 percent to about 9 percent combined hydrogen in the presence of gaseous carbon monoxide, water, and molecular hydrogen at. a temperature of from about 400C. to about 425C, and at a total pressure of from about 2,000 to about 5,000 p.s.i.g.

, 2. A process as in claim I where the CO and hydro-.

gen are derived from producer gas.

3. A process as'in claim l'where the CO-andhydroygen and steam through heated coke. 

2. A process as in claim 1 where the CO and hydrogen are derived from producer gas.
 3. A process as in claim 1 where the CO and hydrogen are derived from producer gas made by passing oxygen and steam through heated coke. 